1. Field of the Invention
The present invention relates generally to a vibration damping device for use in an automotive engine mount or the like, for example, and more particularly, to a fluid-filled type vibration damping device adapted to utilize vibration damping effect exhibited based on flow action of a non-compressible fluid filling the interior.
2. Description of the Related Art
Conventionally, there are known vibration damping devices designed for installation between components that make up a vibration transmission system such as a power unit and a vehicle body, in order to provide vibration damping linkage or vibration damping support between the components. Such vibration damping devices have a structure in which a first mounting member mounted onto one component of the vibration transmission system and a second mounting member mounted onto the other component of the vibration transmission system are elastically connected by a main rubber elastic body.
Moreover, with the aim of further enhancing the vibration damping ability or the like, there have also been proposed fluid-filled type vibration damping devices adapted to utilize vibration damping effect based on flow action of a fluid filling the interior. Such fluid-filled type vibration damping devices include a partition member supported by the second mounting member, a pressure-receiving fluid chamber and an equilibrium fluid chamber formed on either side of the partition member, and an orifice passage interconnecting the pressure-receiving fluid chamber and the equilibrium fluid chamber. Such a device is disclosed in Japanese Unexamined Patent Publication No. JP-A-2009-243510, for example.
In some cases, the fluid-filled type vibration damping device employs a movable plate for switching between permitting and limiting of the fluid flow depending on the input vibration. The movable plate is housed within a housing space formed in the partition member and allowed tiny displacement in the axial direction, while receiving on one side thereof a fluid pressure of the pressure-receiving fluid chamber and on the other side thereof a fluid pressure of the equilibrium fluid chamber. At times of vibration input with a small amplitude, fluid flow will be permitted through the tiny displacement of the movable plate within the housing space. Meanwhile, at times of vibration input with a large amplitude, the movable plate will be pressed against the inside wall face of the housing space, thereby limiting the fluid flow.
However, such a movable plate may cause a problem of generating striking noises by striking against the wall face of the housing space during input of a large-amplitude vibration. In particular, the movable plate abuts with a large surface area during initial abutment, making a heavy impact force by the abutment. Thus, there was a problem that a large striking noise would be generated.